src/stdio/__stdio_read.c

   1 #include "stdio_impl.h"
   2 #include <sys/uio.h>
   3
   4 size_t __stdio_read(FILE *f, unsigned char *buf, size_t len)
   5 {
   6         struct iovec iov[2] = {
   7                 { .iov_base = buf, .iov_len = len - !!f->buf_size },
   8                 { .iov_base = f->buf, .iov_len = f->buf_size }
   9         };
  10         ssize_t cnt;
  11
  12         cnt = iov[0].iov_len ? syscall(SYS_readv, f->fd, iov, 2)
  13                 : syscall(SYS_read, f->fd, iov[1].iov_base, iov[1].iov_len);
  14         if (cnt <= 0) {
  15                 f->flags |= cnt ? F_ERR : F_EOF;
  16                 return 0;
  17         }
  18         if (cnt <= iov[0].iov_len) return cnt;
  19         cnt -= iov[0].iov_len;
  20         f->rpos = f->buf;
  21         f->rend = f->buf + cnt;
  22         if (f->buf_size) buf[len-1] = *f->rpos++;
  23         return len;
  24 }